1. Field of the Invention
The invention relates generally to bone fixation devices, and in particular, bone fixation devices for fusion of the human cervical spine from an anterior approach.
2. Background
Cervical plating systems are used to align and maintain adjacent cervical vertebrae in a selected spatial relationship to facilitate fusion of the vertebrae. Generally, cervical plating systems include plates and screws for aligning and holding vertebrae in a desired position relative to one another. In known plating systems, there have been problems with loosening and failure of the hardware. In particular, there have been problems with the screws migrating from the plate and potentially damaging the patient's throat.
Additionally, there have been problems with “creeping substitution” in known plating systems. In “creeping substitution”, bone at the interface between the graft and vertebrae is removed by natural biological processes prior to the growth of new bone. Although the plates are capable of holding the vertebrae in proper alignment, they tend to hold the vertebrae apart during resorption of the bone, thus forming gaps at the fusion site. Consequently, fusion may not occur. Such failure is known as pseudoarthrosis. When such a failure occurs, the hardware itself may break or become loosened from the spine, and may therefore require further surgical procedures to remove the broken components and to attempt fusion.